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M18 recoilless rifle
The M18 recoilless rifle was a 57mm shoulder fired anti-tank recoilless rifle used by the U.S. Army in World War II and the Korean War. Recoilless rifles are capable of firing artillery-type shells at reduced velocities comparable to those of standard cannon, but with greater accuracy than anti-tank weapons that used unguided rockets, and almost entirely without recoil. The M18 was a breech-loaded, single-shot, man-portable, crew-served weapon. It could be used in both anti-tank and anti-personnel roles. The weapon could be both shoulder fired or stabilized using a monopod. The most stable firing position was from the tripod developed for the water-cooled Browning M1917 machine gun.Jane's Infantry Weapons 1976 page 571. Origins and development During World War II, the U.S. Army's Artillery Section was working on a 105mm recoilless cannon, based on captured German models that used a plastic blow out plug in the cartridge case. At the same time, there was a freelance research by the U.S. Army's Infantry Section of a man-portable recoilless 57mm cannon by two engineers, named Kroger and Musser. Instead of a blowout plug, the infantry section's recoilless cannon used a British development in which the cartridge case had hundreds of small holes in the side walls with a lining of plastic on the inside of the cartridge case walls to keep water and other elements out until the round was fired. Another unique innovation was the use of pre-engraving bands on the 57mm projectile that engaged the barrel's rifling.While many sources claim the pre-engraving on the M18 projectiles drive band in 1943 was a first, the Germans in World War One had this feature on projectiles for their famous Paris Gun. Later it was discovered that pre-engraving the band gave no advantage and future rounds were produced without this feature The belief was this feature would reduce friction on firing, allowing more of the propellant gases to be used to force the shell towards the target and less being used to achieve the recoilless effect and therefore giving their design a much higher muzzle velocity than most recoilless cannon at that time period had achieved.Ian Hogg The Guns 1939-45 page 151 Ballantine Books 1970.With most recoilless cannon, there is a 1-to-9 ratio -- meaning that when the weapon is fired, 1 part of the propellant gases is used to force the shell forward and the other 9 parts of the propellant gases are expelled to the back to counter act that forward force, achieving a recoilless effect. The "Kromuskit", as the new 57mm weapon was called (a word play on the engineers' family names) was officially designated the T15 and first tested in November 1943. The tests proved that the Infantry Section's concept for a recoilless weapon was superior to the Artillery Section's concept and the development of the 105mm weapon was canceled.Weapons and Warfare, p. 879, Vol. 8, 1978. In late 1944, the T15 was redesignated the M18 57mm Recoilless. The cannon and 57mm ammunition were placed in mass production. Four types of ammunition were initially produced: an anti-tank HEAT round, an HE round, a smoke shell using white phosphorus, and a training round.TM 9-1300-204, Ammunition for Recoilless Rifles, p. 9, Washington: Department of the Army, 1959.After World War Two ended, a canister round with a range of 175 meters was also produced. By early 1945, over 2,000 M18 recoilless rifles and 800,000 rounds of ammunition were on order.Ian Hogg The Guns 1939-45 page 151 Ballantine Books 1970. US Service World War II The first fifty''Engineering Design Handbook: Recoilless Rifle Weapon Systems'', p. 1-7, Army Material Command, 15 January 1976. production M18 57mm cannons and ammunition were rushed from the factories to the European Theater in March 1945. Further examples were subsequently sent to the Pacific Theater. The first combat the new cannon saw was with the U.S. Army's 17th Airborne Division near Essen, Germany. While impressed with the performance of the high explosive (HE) warhead, the M18's 57mm HEAT anti-tank round proved to be a disappointment, with only 63.5mm (2.5-in.) of armor penetration at 90 degrees,Jane's Infantry Weapons 1976 page 571.Recoilless Weapons, Office of the Chief of Ordnance, February 1945, p. 7, gives a penetration figure of "up to three inches at 20° obliquity". compared with the older M1A1 Bazooka which had a nominal penetration of nearly 120mm.Terry J. Gander, The Bazooka page 18, The Military Book Club.Unfortunately, even 120mm of penetration was not enough to defeat the frontal armor of most German tanks after 1943.Ian Hogg, The Guns 1939-45, page 79, Ballantine Books 1970: The reason for the disappointing penetration by the M18's 57 mm anti-tank round was the problem any HEAT round has when fired from a cannon that uses rifling to stabilize its projectile: the spin imposed by the rifling degrades the penetrative effect of the HEAT round. In the Pacific Theater, the new lightweight 57 mm cannon was an absolute success as "pocket artillery" for the soldiers of U.S. Army infantry units that were issued the M18. It was first used in the Pacific Theater during the Battle of Okinawa on June 9, 1945, and proved with its HE and WP rounds it was the perfect weapon for the hard fighting that took place against the dug-in Japanese in the hills of that island. The only complaint the U.S. Army had was the lack of sufficient 57 mm ammunition for the M18.Weapons and Warfare, p. 890, Vol. 8, 1978. Korean War Each U.S. rifle company in the Korean War was authorized three M18 recoilless rifles.US Army Forces in the Korean War, Donald W. Boose, p.27, Oxford: Osprey, 2005. Veterans of the Korean War have mentioned the use of the M18 against enemy machine gun nests.rt66.com webpage For anti-tank tasks, however, the M18 was too weak; the T-34 tank was extremely hard to penetrate even for the 2.36 inch (60 mm) Bazooka of World War II which had almost no chance to penetrate it. The only way would have been flank or rear shots. U.S. infantry, initially with very few capabilities against these targets, solved the problem with new weapons like the 3.5 inch (89 mm) M20 Super Bazooka, which was powerful enough to destroy T-34s.www.rt66.com Production and use outside the US The M18 was copied by the People's Republic of China as the Type 36. The U.S. had provided Nationalist China the blueprints for the weapon. When the communists seized the factory, they took advantage of the facilities and blueprints to make their own copy of the weapon.Ian Hogg, Jane's Infantry Weapons, pp. 693 & 695, 1984-85, London: Jane's Publishing Company Ltd., 1984. China provided the Vietnamese communists the Type 36 in 1963 for use in the Vietnam War.Simon Dunstan, Vietnam Tracks, p. 56, Oxford: Osprey Publishing, 2004. Tanzania was also a user of the Type 36. In a strange twist, the Chinese version of the M18 can fire both U.S. and Chinese manufactured ammunition, but U.S. made M18s can not fire Chinese ammunition.Jane's Infantry Weapons 1976 page 571. As late as 1984, the M18 57 mm recoilless rifle was still being produced under license in Brazil by Hydroar in São Paulo.Ian Hogg, Jane's Infantry Weapons, pp. 693 & 695, 1984-85, London: Jane's Publishing Company Ltd., 1984. Sources and notes External links * U.S. 57mm Recoilless Rifle at Inert-Ord.net * New Kickless Cannon for GIs Popular Science 1945 Category:Anti-communist forces weapons Category:Weapons of the Vietnam War